This invention relates to engine valve trains and lubrication systems.
It is known in the art to lubricate the components of engine valve trains to control wear of the relatively moving parts. Commonly, pressure lubrication is utilized, although some systems rely on oil spray or mist. It is also known to use pressurized lubricant to operate control devices, such as switching lifters for valve deactivation and cam phasers for varying valve timing. These devices may require increasing lubricant flow or maintaining prescribed oil pressure to assure their proper operation. However, it is desired to limit requirements for increased oil flow and pressure to avoid parasitic losses in the lubricant system that reduce overall engine efficiency.
The present invention provides a modified valve train for an internal combustion engine which improves engine efficiency by selectively reducing the flow of lubricating oil to the nonmoving parts of the valve train during cylinder deactivation.
Definitions: As used in the following summary, description, claims and abstract, the term pivot and its related terms, such as pivoting, pivotally, pivotable, etc. are intended to refer exclusively to oscillating motion of a member, such as a rocker arm, or a joint, such as a push rod to rocker arm connection as shown in the drawings illustrating the present invention and as these terms are commonly used in reference to such valve train components. Where a rotational joint or motion is intended, the term rotate and variations thereof are utilized to distinguish from oscillatory pivoting motion as referred to above.
Under normal operating conditions, oil is pumped through the engine to provide lubrication for all of the moving components of the valve train. Cylinder deactivation may be accomplished by switching valve lifters which are operated to selectively stop actuation of the intake and exhaust valves of the deactivated cylinders. This invention stems from the recognition that stopping or reducing lubrication to the nonmoving components in the valve train during cylinder deactivation can reduce parasitic losses from excess lubricant flow while continuing to provide necessary lubrication to the valve train when the cylinders are again activated.
In a preferred embodiment, the valves are actuated by cam following switching lifters connected through hollow pushrods with rocker arms that actuate the valves. Oil from the lifters is delivered through a pivotable connection between the pushrods and the rocker arms. Openings in the connection are misaligned when the valves are closed to limit or cut off oil flow. Opening of the valves aligns the openings to provide oil flow to the rocker arms when the valves are opening and closing.
Cutting off or limiting oil flow to the rocker arms when the valves are closed significantly reduces parasitic oil flow in the lubrication system and thereby increases engine efficiency. The arrangement not only limits oil flow to the rocker arms of deactivated cylinders but also limits (or cuts off) oil flow to the rocker arms of active cylinders when their valves are closed, allowing full lubrication flow only when the valve are being opened and closed. Thus, the invention can be used to increase lubrication system efficiency in engines without cylinder deactivation as well as in those having this feature.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.